• Steel and Composite Structures
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• v.27 no.3
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• pp.273-283
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• 2018

Nonlinear low velocity impact response of sandwich beam with laminated composite face sheets and soft core is studied based on Extended High Order Sandwich Panel Theory (EHSAPT). The face sheets follow the Third order shear deformation beam theory (TSDT) that has hitherto not reported in conventional EHSAPT. Besides, the two dimensional elasticity is used for the core. The nonlinear Von Karman type relations for strains of face sheets and the core are adopted. Contact force between the impactor and the beam is obtained using the modified Hertz law. The field equations are derived via the Ritz based applied to the total energy of the system. The solution is obtained in the time domain by implementing the well-known Runge-Kutta method. The effects of boundary conditions, core-to-face sheet thickness ratio, initial velocity of the impactor, the impactor mass and position of the impactor are studied in detail. It is found that each of these parameters have significant effect on the impact characteristics which should be considered. Finally, some low velocity impact tests have been carried out by Drop Hammer Testing Machine. The contact force histories predicted by EHSAPT are in good agreement with that obtained by experimental results.

• Steel and Composite Structures
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• v.31 no.5
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• pp.469-488
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• 2019

We in this paper study nonlinear bending of a functionally graded porous nanobeam subjected to multiple physical load based on the nonlocal strain gradient theory. For more reasonable analysis of nanobeams made of porous functionally graded magneto-thermo-electro-elastic materials (PFGMTEEMs), both constituent materials and the porosity appear gradient distribution in the present expression of effective material properties, which is much more suitable to the actual compared with the conventional expression of effective material properties. Besides the displacement function regarding physical neutral surface is introduced to analyze mechanical behaviors of beams made of FGMs. Then we derive nonlinear governing equations of PFGMTEEMs beams using the principle of Hamilton. To obtain analytical solutions, a two-step perturbation method is developed in nonuniform electric field and magnetic field, and then we use it to solve nonlinear equations. Finally, the analytical solutions are utilized to perform a parametric analysis, where the effect of various physical parameters on static bending deformation of nanobeams are studied in detail, such as the nonlocal parameter, strain gradient parameter, the ratio of nonlocal parameter to strain gradient parameter, porosity volume fraction, material volume fraction index, temperature, initial magnetic potentials and external electric potentials.

• Advances in aircraft and spacecraft science
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• v.5 no.1
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• pp.21-49
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• 2018

In this paper, geometric nonlinear bending characteristics of single wall carbon nanotube reinforced composite (SWCNTRC) doubly curved shell panels subjected to uniform transversely loadings are investigated. The nonlinear mathematical model is developed for doubly curved SWCNTRC shell panel on the basis of higher-order shear deformation theory and Green- Lagrange nonlinearity. All nonlinear higher order terms are included in the mathematical model. The effective material properties of SWCNTRC are estimated by using Eshelby-Mori-Tanaka micromechanical approach. The governing equation of the shell panel is obtained using the total potential energy principle and a Newton-Raphson iterative method is employed to compute the nonlinear displacement and stresses. The present results are compared with published literature. The effect of SWCNT volume fraction, width-to-thickness ratio, radius-to-width ratio (R/a), boundary condition, linear and nonlinear deflection, stresses and different types of shell geometry on nonlinear bending response is investigated.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1990.04a
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• pp.59-64
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• 1990

The cable structures undergo large deformation because of its highly flexibility. Therefore, we must take account of its geometric nonlinearity before analysis and find the equiribrated shape of cable structures. To solve these problems, a numerical procedures included nonlinear near theory which is applicable to general cable net, flexible transmission lines and suspended cable roofs, are presented in this paper. Now, this procedures are devided two parts : the one is to obtain the equibrated shape and stress of the cable structures applied uniform load by flexibility iteration method, the other is to analysis the equibrated structures subjected to nodal external forces by nonlinear finite element mothed. Its accuracy and efficiency are found to be comparable to some of other method and, in some aspect, it is mere applicable to cable structures.

• Wind and Structures
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• v.27 no.6
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• pp.369-380
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• 2018

In this research work, nonlinear thermal buckling behavior of functionally graded (FG) plates is explored based a new higher-order shear deformation theory (HSDT). The present model has just four unknowns, by using a new supposition of the displacement field which enforces undetermined integral variables. A shear correction factor is, thus, not necessary. A power law distribution is employed to express the disparity of volume fraction of material distributions. Three kinds of thermal loading, namely, uniform, linear, and nonlinear and temperature rises over z-axis direction are examined. The non-linear governing equations are resolved for plates subjected to simply supported boundary conditions at the edges. The results are approved with those existing in the literature. Impacts of various parameters such as aspect and thickness ratios, gradient index, type of thermal load rising, on the non-dimensional thermal buckling load are all examined.

• Steel and Composite Structures
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• v.33 no.2
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• pp.245-259
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• 2019

The present study aims to investigate the ultimate strength and geometric nonlinear behavior of composite plates containing initial imperfection subjected to combined end-shortening strain and lateral pressure loading by using a semi-analytical method. In this study, the first order shear deformation plate theory is considered with the assumption of large deflections. Regarding in-plane boundary conditions, two adjacent edges of the laminates are completely held while the two others can move straightly. The formulations are based on the concept of the principle of minimum potential energy and Newton-Raphson technique is employed to solve the nonlinear set of algebraic equations. In addition, Hashin failure criteria are selected to predict the failures. Further, two distinct models are assumed to reduce the mechanical properties of the failure location, complete ply degradation model, and ply region degradation model. Degrading the material properties is assumed to be instantaneous. Finally, laminates having a wide range of thicknesses and initial geometric imperfections with different intensities of pressure load are analyzed and discuss how the ultimate strength of the plates changes.

• Steel and Composite Structures
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• v.46 no.6
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• pp.759-772
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• 2023

This manuscript presents a comprehensive mathematical model to investigate buckling stability and postbuckling response of bio-inspired composite beams with helicoidal orientations. The higher order shear deformation theory as well as the Timoshenko beam theories are exploited to include the shear influence. The equilibrium nonlinear integro-differential equations of helicoidal composite beams are derived in detail using the energy conservation principle. Differential integral quadrature method (DIQM) is employed to discretize the nonlinear system of differential equations and solve them via the Newton iterative method then obtain the response of helicoidal composite beam. Numerical calculations are carried out to check the validity of the present solution methodology and to quantify the effects of helicoidal rotation angle, elastic foundation constants, beam theories, geometric and material properties on buckling, postbuckling of bio-inspired helicoidal composite beams. The developed model can be employed in design and analysis of curved helicoidal composite beam used in aerospace and naval structures.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.2
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• pp.29-36
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• 2009

The present study emphasizes a nonlinear model to predict the shear behaviour of reinforced concrete interior beam-column joints. To model the shear behaviour of a panel zone in the beam-column joint, a modified softened truss model theory for in-plane shear prediction was introduced. This relationship was changed to define the characteristics for the rotational spring to represent the shear deformation in the joint by an equivalent moment-rotation relationship from the joint equilibrium. The analysis model was compared with experiments on reinforced concrete interior beam-column joints that were subjected to axial and shear forces, and the current model was found to accurately predict not only the shear force but also the shear deformation in the joint.

• Steel and Composite Structures
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• v.34 no.2
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• pp.279-288
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• 2020

The computational post-buckling strength of the tilted sandwich composite shell structure is evaluated in this article. The computational responses are obtained using a mathematical model derived using the higher-order type of polynomial kinematic in association with the through-thickness stretching effect. Also, the sandwich deformation behaviour of the flexible soft-core sandwich structural model is expressed mathematically with the help of a generic nonlinear strain theory i.e. Green-Lagrange type strain-displacement relations. Subsequently, the model includes all of the nonlinear strain terms to account the actual deformation and discretized via displacement type of finite element. Further, the computer code is prepared (MATLAB environment) using the derived higher-order formulation in association with the direct iterative technique for the computation of temperature carrying capacity of the soft-core sandwich within the post-buckled regime. Further, the nonlinear finite element model has been tested to show its accuracy by solving a few numerical experimentations as same as the published example including the consistency behaviour. Lastly, the derived model is utilized to find the temperature load-carrying capacity under the influences of variable factors affecting the soft-core type sandwich structural design in the small (finite) strain and large deformation regime including the effect of tilt angle.

• Structural Engineering and Mechanics
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• v.18 no.4
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• pp.517-539
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• 2004

Many types of passive control devices have been recognized as effective tools for improving the seismic resistance of structures. A lot of past research has been carried out to study the response of structures equipped with energy-absorbing devices by assuming that the behavior of the beam-column systems are linearly elastic. However, linear theory may not be adequate for beams and columns during severe earthquakes. This paper presents the results of research on the nonlinear responses of structures with and without added passive devices under earthquakes. A new material model based on the plasticity theory and the two-surface model for beams and columns under six components of forces is proposed to predict the nonlinear behavior of beam-column systems. And a new nonlinear beam element in consideration of shear deformation is developed to analyze the beams and columns of a structure. Numerical results reveal that linear assumption may not be appropriate for beams and columns under seismic loadings, especially for unexpectedly large earthquakes. Also, it may be necessary to adopt nonlinear beam elements in the analysis and design process to assure the safety of structures with or without the control of devices.